I know you mentioned the client passed, but in case this comes up again - shivers horses need a very specific kind of management. Extra vitamin E supplementation, a very patient farrier, and as much turnout as possible. I wouldn’t even consider a shivers horse unless I could get them on 24/7, preferably on a grass pasture versus dry lot. Some need specific trailering because they can’t back off a step-up or straightload easily.
I’ve had mixed success with shivers, the price tag should always reflect that the horse has a neurological disease, and keep in mind that sometimes retirement is forced earlier than anticipated if the horse is the sort that needs hind shoes to be comfortable. Or can’t be trailered…